1. Field of the Invention
The present invention relates to a process for the viscosification of an organic liquid which includes the steps of forming two solvent systems of an organic liquid or oil and a polar cosolvent, the polar cosolvent being less than about 15 weight percent of the solvent systems, a viscosity of both solvent systems being less than about 1,000 cps; dissolving an anionic polymer such as neutralized sulfonated polymer (water insoluble) in one of the solvent systems to form a first solution, and dissolving a cationic polymer such as a copolymer of vinyl pyridine, a concentration of the neutralized sulfonated polymer in the first solution being about 0.2 to about 10 weight percent, a concentration of the copolymer of vinyl pyridine in the second solution being about 0.2 to about 10 weight percent, the viscosity of both solutions being less than about 2,000 cps; mixing both solutions together to form a solution of an interpolymer complex of sulfonated polymer and vinyl pyridine copolymer, and admixing or contacting said solution of said interpolymer complex with about 5 to about 500 volume percent water, the water being immiscible with the organic liquid and the polar cosolvent transferring from the organic liquid to the water phase, thereby causing the polymer containing phase to gel (i.e. thicken).
2. Description of the Prior Art
There are many applications for very viscous or gelled solutions which are quite diverse. There are also a number of physical and chemical techniques for preparing such systems. The present invention is concerned with a process for gelling a fluid system by contacting the fluid system with a relatively low viscosity, organic liquid solution of interacting polymers. The potential applications for this process and the products derived therefrom will be evident in the instant application. Some of these applications are as a viscosifier for hydrocarbon solutions, such as a shut-off process in grouting operations, a water shut-off technique in oil well applications and a spacer or soluble plug in oil well applications.
The instant invention differs from a number of applications, Ser. Nos. 223,482; 136,837; and 106,027, filed by Robert Lundberg et al, one of the instant inventors. Respectively, U.S. Pat. Nos. 4,361,658; 4,322,329 and 4,282,130. These previously filed applications were directed to the gelling of the organic liquid by a water insoluble, neutralized sulfonated polymer whereas the instant invention is directed to the gelling of an organic fluid by an interpolymer complex.
The instant invention describes a process which permits (1) the preparation of polymer solutions of interpolymer complexes in organic liquid having reasonably low viscosities (i.e., less than about 200 cps); and (2) the preparation of extremely viscous solutions or gels of the organic fluid from such solutions by a process of mixing or contacting water with the polymer solution. These operations are achieved by the use of the appropriate concentration; 0.2 to 10.0 weight percent of water insoluble, interpolymer complexes, having low concentrations of ionic groups present.
In the instant process, the role of the polar cosolvent is that of solvating the ionic groups while the main body of the solvent interacts with the polymer backbone. For example, xylene is an excellent solvent for the polystyrene backbone and when combined with 5 percent methanol will dissolve, readily and rapidly, the previous example of lightly sulfonated polystyrene.
The remarkable and surprising discovery of the instant invention is that when small (or large) amounts of water are combined and mixed with solutions of ionic polymers dissolved at low concentrations (about 0.2 to 10 weight percent) in such mixed solvent systems as those described above, a phase transfer of the cosolvent occurs from the nonpolar organic liquid phase to the water phase, thus by causing the polymer containing phase to gel (i.e. thicken). Indeed, it is possible to achieve increases in viscosity of the polymer solution by factors of 10.sup.3 (1,000) or more by the addition of only 5 to 15 percent water based on the polymer solution volume. This unusual behavior is postulated to arise from the removal of the polar cosolvent from the organic liquid phase into the separate aqueous phase.